It is now conventional to produce shells for two-piece cans by a drawing and ironing technique, such as in the manner described in U.S. Pat. No. 3,360,157. While the method and apparatus described in that patent, and elsewhere in the art, are entirely satisfactory under many circumstances, and indeed are in widespread use, in some instances certain deficiencies or difficulties are found to arise in practice.
More specifically, there has been found to be a lack of sufficient predictability and dependability in the ironing dies heretofore employed, making uniform production a very difficult matter. Moreover, the existing die configurations have tended to cause defects in the articles, sometimes destroying them and, in extreme cases, damaging the forming apparatus. Finally, such dies have not exhibited desirable levels of durability, and have required excessive maintenance to keep them in proper working condition. By-and-large, it is believed that the deficiencies and difficulties of the prior art dies are due essentially to the profile of the forming opening thereof.
Accordingly, it is an object of the present invention to provide a novel metal forming die, which affords predictable and dependable operation to produce articles of highly uniform configuration and dimensions, notwithstanding variations in the material of the blank from which the article is formed.
It is also an object of the invention to provide such a die which affords excellent control of the forming operations, to permit highly efficient manufacture while minimizing damage to the articles being produced, and to the forming apparatus.
It is still another object of the invention to provide a novel die having the foregoing features and advantages, which die is more durable and requires less maintenance than comparable dies heretofore provided.